I have an install wizard for product X with steps A > B > C>...>G, where C has a single drop-down selector. The drop-down selector in C either has one option, or many options: this is determined by the optional configuration of a separate product, Y. If Y has been configured, you would have multiple options. If Y has not been configured, you would only have one option, the built-in default. I expect only about 25% of users to want Y configured.
In cases where Y has not been configured, and thus there is only one option for the selector, is it appropriate to omit page C?
My concern with leaving the page in is that this is a feature many users don't care about, and I would then have entire additional page most users don't need. At the moment, there is not another appropriate page in the wizard for the selector.
I've seen many posts here that advocate against hiding elements that users can sometimes access, but those have discussed menu items or buttons, rather than pages in a multi-step process.